1. Field of the Invention
The present invention generally relates to high purity electrolytic copper and a method of producing the high purity electrolytic copper, and more particularly, to a method of electrowinning high purity copper in a halide bath.
2. Description of the Related Art
Copper electrowinning is performed to leach copper from ores and other materials in a solution, and to electrolytically reduce the leached copper ions to form electrolytic copper to be put on the market. Copper electrowinning methods of this type include a method of electrowinning copper in a sulfate bath and a method of electrowinning copper in a halide bath.
The method of electrowinning copper in a sulfate bath has been put into practice, and it has been proved that electrolytic copper of the same quality as the quality of electrorefining copper, which is the normal electrolytic copper, can be obtained by the method. On the other hand, by the method of electrowinning copper in a halide bath, electrodeposited metals in plate-like form cannot be obtained, and the electrodepositing form varies from particle form to dendritic form. Under such conditions, electrolytic copper that has high enough quality to be put on the market cannot be obtained. This has constituted a great hindrance in leaching ores and electrowinning copper through hydrometallurgical processing in a chloride bath that excels in copper leaching ability and copper solubility. Particularly, as sulfuric acid is not very effective for the leaching of chalcopyrite, it is desirable to perform leaching in a chloride bath. However, the above mentioned reason has remained a great hindrance in doing so.
When electrowinning is performed in a halide bath, a large quantity of additives such as gelatin is conventionally used with a current density of 100 A/m2 or lower, so as to obtain electrodeposited metals in plate-like form. However, productivity is very low with such a low current density, and sufficient electrodeposition in plate-like form cannot be expected with a higher current density. U.S. Pat. No. 5,487,819 discloses a method of producing high quality electrolytic copper through the formation of dendrites using dimpled cathodes with a current density of 500 A/m2 to 1000 A/m2 (Intec process). However, the method has not proved to be successful in steady production of electrolytic copper having a purity corresponding to the purity of electrorefining copper. Furthermore, the dendrite deposition presents a problem of the deposited copper in dendritic form being hooked or hung in electrolytic cells, making it difficult to scrape off and remove the deposited copper from electrodes.